When a touchstone touches iron, it turns the iron to gold. Parvata Muni called Narada Muni a touchstone because by his touch the hunter, who was the lowest among men, became an elevated and perfect Vaisnava. Srila Bhaktivinoda Thakura said that the position of a Vaisnava can be tested by seeing how good a touchstone he is, that is, by seeing how many Vaisnavas he has made during his life. A Vaisnava should be a touchstone so that he can convert others to Vaisnavism by his preaching, even though people may be fallen like the hunter.